Re: about syscall again~

* yuanbor ([email protected]) wrote:
> 
>    I execute getegid syscall twice, and the trace list below.
> 
>    What I wanna get is the elapsed time between the time enter the kernel
>    mode and the time return to user mode. According to the trace, I get
>    this time:
> 
> 
> 
>    [1]the second syscall_entry time - the first syscall_entry
>    time:3265.985720957-3265.985719068=1889
> 
>    [2]syscall_exit - syscall_entry : 3265.985720157 - 3265.985719068=1089
> 
> 
> 
>    my question is that whether the syscall_exit time is the time exec
>    flow return from kernel mode to user mode or the time the kernel
>    starts to handle the exit code?
> 
> 

Please have a look at the kernel source for this. The marker is in
syscall_trace(). This is called within the kernel a bit before returning
to user space.

Mathieu

> 
> 
> 
> 
> 
> 
> 
>    kernel_arch.syscall_entry: 3265.985719068
>    (/home/yuanbor/trace/syscall/1184337598/cpu_0), 2710, 2710,
>    ./syscall_gettimeofday, UNBRANDED, 2664, 0x0, SYSCALL { getegid32,
>    -7152 }
> 
>    locking.hardirqs_off: 3265.985719566
>    (/home/yuanbor/trace/syscall/1184337598/cpu_0), 2710, 2710,
>    ./syscall_gettimeofday, UNBRANDED, 2664, 0x0, SYSCALL { 3222293953 }
> 
>    locking.hardirqs_on: 3265.985719853
>    (/home/yuanbor/trace/syscall/1184337598/cpu_0), 2710, 2710,
>    ./syscall_gettimeofday, UNBRANDED, 2664, 0x0, SYSCALL { 3222294237 }
> 
>    kernel_arch.syscall_exit: 3265.985720157
>    (/home/yuanbor/trace/syscall/1184337598/cpu_0), 2710, 2710,
>    ./syscall_gettimeofday, UNBRANDED, 2664, 0x0, USER_MODE
> 
>    locking.hardirqs_on: 3265.985720401
>    (/home/yuanbor/trace/syscall/1184337598/cpu_0), 2710, 2710,
>    ./syscall_gettimeofday, UNBRANDED, 2664, 0x0, USER_MODE { 3222294012 }
> 
>    kernel_arch.syscall_entry: 3265.985720957
>    (/home/yuanbor/trace/syscall/1184337598/cpu_0), 2710, 2710,
>    ./syscall_gettimeofday, UNBRANDED, 2664, 0x0, SYSCALL { getegid32,
>    -7152 }
> 
>    locking.hardirqs_off: 3265.985721336
>    (/home/yuanbor/trace/syscall/1184337598/cpu_0), 2710, 2710,
>    ./syscall_gettimeofday, UNBRANDED, 2664, 0x0, SYSCALL { 3222293953 }
> 
>    locking.hardirqs_on: 3265.985721609
>    (/home/yuanbor/trace/syscall/1184337598/cpu_0), 2710, 2710,
>    ./syscall_gettimeofday, UNBRANDED, 2664, 0x0, SYSCALL { 3222294237 }
> 
>    kernel_arch.syscall_exit: 3265.985721905
>    (/home/yuanbor/trace/syscall/1184337598/cpu_0), 2710, 2710,
>    ./syscall_gettimeofday, UNBRANDED, 2664, 0x0, USER_MODE
> 
>    locking.hardirqs_on: 3265.985722148
>    (/home/yuanbor/trace/syscall/1184337598/cpu_0), 2710, 2710,
>    ./syscall_gettimeofday, UNBRANDED, 2664, 0x0, USER_MODE { 3222294012 }

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-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
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